Combustible compositions, firelighters, barbeque starters and firelogs

Abstract

 A combustible composition comprising a fuel in the form of a wax, gel, or paste having dispersed therein an inorganic, particulate, non-combustible solid serving to decrease the rate at which the fuel burns on combustion of the composition, and optionally a combustible filler material, the composition being such that it does not flow substantially during combustion.

Description

[0001] The present invention relates to combustible compositions and includes compositions which in relatively small pieces are useful as firelighters as well as compositions which may be used to make artificial firelogs. The compositions of the invention may also be used as fuel.

[0002] Known combustible compositions include those compositions which are used as firelighters, charcoal igniters and artificial fire logs. Certain of these compositions comprise fuel in the form of a wax, gel or paste, optionally filled with organic, combustible solids such as wood waste, (e.g. wood flour or wood shavings).

[0003] United States Patent Specification No.4165968 discloses a gelled alcohol containing expanded perlite for the special purpose of forming a thin surface coating on charcoal briquettes to make them easily lightable. This alcohol gel composition would not be suitable for use in bulk as a firelighter because it would flow during combustion producing a large burning surface area and hence burning for only a short period. The purpose of the expanded perlite in the composition is to give the coating produced on charcoal a rough surface which acts as a wick to give easy ignition, rapid flame spread and hence an increased rate of fuel consumption.

[0004] We have found that the incorporation of inorganic solids into compositions which do not flow during combustion, and which therefore are themselves useful as fuel, firelighters or barbeque starters, can produce a decrease in the rate at which the fuel content of the combustible composition is consumed..

[0005] The present invention now provides a combustible composition comprising a fuel in the form of a wax, or paste having dispersed therein an organic, particulate, non-combustible solid serving to decrease the rate at which the fuel burns on combustion of the composition, and optionally a combustible filler material, the composition being such that it does not flow substantially during combustion; provided that when the composition comprises a combustible filler material and the composition is one which has been formed hot, the composition contains from O.5 to 6% by weight of the inorganic, particulate, non-combustible solid.

[0006] The fuel in wax, gel, or paste form may for instance be an animal, mineral or vegetable wax, a gel formed from a combustible liquid or liquefiable fuel e.g. a hydro carbon such as kerosene or an alcohol, or a paste formed .by emulsifying an oil in water.

[0007] The combustible composition may accordingly comprise a compacted mixture of a combustible organic solid, such as wax, wood waste, and the inorganic solid. The wax which serves to bind such a composition together may be a solid or semi-solid wax. The composition may optionally contain a combustible liquid such as kerosene, distillate, gas oil, white spirit, sump oil or oils of vegetable origin such as may be used in the paints and plastics industries, and/or oils or fats of animal origin. Other fuel materials which may optionally be included are waste materials from the plastics industry including waste polymers such as atactic polypropylene.

[0008] Compositions of the above type may be formed into large pieces suitable as artificial firelogs.

[0009] A further type of combustible composition according to the invention may comprise as well as the inorganic solid a gelled combustible liquid, e.g. a liquid hydrocarbon such as kerosene and/or vegetable or animal derived oils. The liquid may be. gelled by means of a suitable thickener such as metal soap including aluminium stearates and octanoates, carboxymethyl cellulose, hydroxymethyl cellulose, hydroxypropyl cellulose, nitrocellulose, gums such as xanthan, arabic, tragacanth, shellacs, rosin, lignosulphates, tall oil cuts, quebracho extracts, caseinates, gelatin, higher alcohols, synthetic polymers such as polybutabols, ethylene copolymers, polyvinyl alcohols, polyvinyl acetate, vinyl cellulose, polyketones, polyesters, phenoxy resins, polymeric diols, vinyl butyral resins, vinyl acetate/polyvinyl chloride copolymers, _N-cocohydroxybutyramide, polyamides and inorganics such as silica xerogel (known as "fumed silica"), thickening clays such as bentonite, laponite, montmorillonite and mixtures thereof. The gelling agent is selected so that composition will not flow during combustion to a significant extent.

[0010] The composition may contain a combustible organic solid such as wood waste or peat or plastics waste. Waxes may be incorporated into such compositions to act as additional fuel and in some cases to help bind the composition. Conventional products of this general type but lacking the inorganic solid characteristic of the invention are known as "brown firelighters".

[0011] Examples of compositions according to the invention include an alcoholic gelled by the use of a thickener as described above e.g. soap and/or silica xerogel (known as "fumed silica") as the fuel in combination with the inorganic solid. Kerosene or other hydrocarbon fuel or other oil may be used in place of the alcohol.

[0012] A further type of composition according to the invention may comprise the inorganic solid and a water- immiscible fuel e.g. hydrocarbon oil or other oil, emulsified with water, to form a stiff paste e.g. by the action of suitable emulsifying agents optionally in conjunction with application of high shear which has the effect of thickening the emulsion. Such an emulsion serves to provide the fuel in paste form.

[0013] The inorganic solid is preferably insoluble in water.

[0014] Preferably, the inorganic non-combustible particulate solid has low bulk density, for example less than 0.4 g.cc ^l.

[0015] Examples of materials found to be suitable are chalk, china clay, diatomaceous earth, perlite rock, sand, FILLITE which is a particulate solid separated from boiler ash and has the form of microspheres, vermiculite, talc, and exfoliated vermiculite.

[0016] Preferably, the density of the inorganic non-combustible particulate solid is similar to or less than that of the liquefiable fuel component. More preferably, the density of the solid is much less than that of the liquefiable fuel component.

[0017] Preferably, the particles of the inorganic non-combustible solid are impermeable to liquids, that is to say, the liquefiable fuel cannot completely penetrate the interior of the particles. This may be achieved by the use of solids that have a liquid-impermeable "skin" such as FILLITE, or by coating the particulate material with a barrier material which may be a polymeric coating composition such as an alkyd resin or nitrocellulose or a heavy metal soap, a silicone, or a silicate, or a viscous non-drying oil or a drying oil.

[0018] In order to minimize the opportunity for the solid to absorb liquid fuel, it is preferred that the solid be added to the other ingredients shortly before the composition becomes too stiff to allow the introduction of the solid.

[0019] The amount of the inorganic non-combustible solid that may be included varies depending upon the inorganic non-combustible solid used and normally would not exceed 20% w/w. Usually up to 12% w/w of the total composition may be used. Preferably, the amount is less than 8% w/w and 1% to 6% w/w is especially preferred.

[0020] The combustible composition may contain, in addition to the inorganic non-combustible particulate solid a proportion of combustible particulate material. Typical of such materials are :- wood wastes including wood flour, wood shavings or comminuted compressed wood wastes; peat in dried native or dried and comminuted, precompressed form; coal fines; lignite; waste paper or cardboard; comminuted plant material such as comminuted compressed wastes from grain crops optionally partly hydrolysed, seeds such as linseed, rapeseed and millet which may be used whole or crushed including oil-mill waste, or seed hulls such as coconut husk, walnut shells and peach stones preferably in comminuted form; or mixtures thereof. All things which contribute significantly to the calorific value of the end product be it firelighter, barbeque starter or artificial firelog may be used.

[0021] Generally the proportion of such combustible solid material in the compositions of the invention will not exceed 80% by weight and more preferably will not be more than 70% by weight.

[0022] Preferably, the amount of inorganic non-combustible particulate solid included does not exceed 12% w/w based on the final product. In those cases where a particulate organic combustible material is included, the amount of inorganic solid preferably does not exceed 8% w/w by weight of the final composition and is preferably 0.5% to 6% w/w.

[0023] Howeverer, with some inorganic non-combustible particulate solids, especially in artifical firelog compositions these amounts may be increased up to 20%.

[0024] The composition according to the invention may generally be used as firelighters or charcoal igniters. Those compositions which are not self-supporting solids may be put up in sachets to provide unit doses or may be filled into collapsible tubes for dispensing in such doses as are desired.

[0025] Those compositions possessing sufficient structural integrity may suitably be made into artificial firelogs and these may contain up to 20% w/w fillite providing a crackle effect.

[0026] The composition of the invention may be prepared in a variety of ways depending upon whether the final product is to be used as an ignition product for fires on the one hand or barbeque starters on the other hand or an artificial firelog. The manufacture of such product types is well understood and the incorporation of the selected inorganic non-combustible particulate material may be effected by mixing at a suitable stage depending upon whether the final composition is to include a mechanical mixture of fuel and solid organic combustible material, a gelled fuel without wood waste or a brown firelighter type product.

[0027] If the final product is to be of the first type, the inorganic non-combustible particulate material, optionally precoated with surface treatment material, may be admixed together with or separately from the solid organic combustible material into the fuel with stirring usually at slightly elevated temperature especially in those cases where a relatively high melting point fuel is employed. In some cases it may be suitable to slurry the inorganics optionally admixed with the fuel in liquid form and introduce them as a fluid into the final blend.

[0028] Where the final product is to be a gelled . product, preferably the gel is formed first from suitable components, that is a thicknener such as fumed silica or a soap and a fuel component in liquid form, for example an alcohol or kerosene. The inorganic component may then be admixed therewith with stirring to achieve uniform distribution. However the inorganic solids may be dispersed ih the fuel whilst it is in liquid form and then the mixture may be gelled by addition of soap or its formation in situ. It has been observed that the final product is often of stiffer consistency than the initially formed gel.

[0029] Preferably, when the soap is used for the gelling, the soap is a C12 - C18 fatty acid derived soap. Preferably the soap is a saturated one since these give firmer gels. An Example of a preferred material is sodium stearate. Heavier metal soaps such as aluminium stearate may additionally or alternatively be used. The fuel does not have to be normally liquid and materials such as slack wax may be gelled with soap. Preferred proportions of fuel and soap are 3 to 25% by weight soap, more preferably 8 to 15% by weight soap, based on the weight of fuel and soap.

[0030] In the case of a brown firelighter type of final product where, for example kerosene or other combustible liquid is gelled, as with a soap, and mixed with wood waste to achieve a shape-retaining final solid that may be cut into blocks or moulded, the solid, particulate non-combustible material may be mixed with the gelling fuel component.

[0031] Alternatively the inorganic solid may be mixed with the fuel in liquid form and the mixture may be gelled e.g. by addition of soap or formation of soap in situ. The freshly formed composition may be allowed to stand until of satisfactory consistency if it is desired to be cut into blocks subsequently. Alternatively, the mixture may be moulded into individual blocks and wrapped when set to handlable consistency.

[0032] Another means of presenting the product is in sachets, i.e. sealed envelopes which closely fit the outer surfaces of the blocks when set.

[0033] Where such a composition is to be used as an artificial firelog suitably large pieces may be moulded as by extrusion or compaction and optionally wrapped.

[0034] Combustible compositions of the present invention are preferably match ignitable.

[0035] The invention will now be illustrated by the following Examples in which parts are by weight:-

Example 1

[0036] An isopropanol gel composition was prepared by adding 5 parts of CABOSIL M-5, a fumed silica, to 95 parts isopropanol with stirring.

[0037] 2 parts of a non-combustible inorganic particulate solid was added with stirring to 100 parts of the gel.

[0038] 30g portions of the resultant pasty solid were ignited in a standard laboratory dish of diameter 65 mm and depth 12 mm and the burning time from ignition to self. extinguishing end point was observed in each case. A

[0039] control lacking non-combustible inorganic particulate solid was run for comparison. The results obtained were as follows:-

[0040] Thus it may be. seen that in each case the burning time was protracted as compared with the control.

Example 2

[0041] An ethanol gel composition was prepared in analogous manner to that of Example 1 using industrial methylated spirit containing 5% w/w CABOSIL M-5 fumed silica.

[0042] Dupre vermiculite Grade DF (exfoliated) was added to portions of this gel at increasing levels and the burning times were observed for 30 g aliquots of the soft, pasty solid resulting in a standard laboratory dish as in Example 1 with a control.

[0043] The results obtained were as follows:-

[0044] Whilst there is no significant protraction in burning time in most of these samples compared with the control, it is clear that at the same time there is no significant diminution thereof yet the amount of liquefiable fuel present decreases with increase in concentration of the vermiculite. That is to say an improvement in efficiency of burning fuel occurs.

[0045] No difference in flame characteristics were observed.

Example 3

[0046] An ethanol gel was prepared from industrial methylated spirits by admixing with stearic acid at 10% w/w level with stirring and warming gently.

[0047] 2 parts exfoliated vermiculite (DUPRE Grade DF) was added to 98 part of the gel so-produced to produce a stiff paste and the burning time of 20 g aliquots was assessed in a manner analagous to Example 1 using a control lacking vermiculite.

[0048] The burning time of the control was 10.50 minute and that if the vermiculite containing gel was 14.5 minute. Thus the efficiency of burning alcohol increases on adding vermiculite at 2% level from 0.58 min per gram alcohol to 0.82 min per gram alcohol.

Example 4

[0049] A kerosene soap gel containing wood waste and vermiculite was prepared by first heating a mixture of 72 parts kerosene and 10 parts stearic acid to 50°C until all the acid is dissolved whilst mixing using a propeller blade mixer.

[0050] 3 parts of a 50% aqueous sodium hydroxide was then dissolved in the solution with stirring. To 83 parts of this mixture 17 parts of premixed wood flour (15 parts) and exfoliated vermiculite (DUPRE Grade DF) (2 parts) were added in a dough mixer to mix with the above solution uniformly. The resultant suspension was poured into moulds and lightly tamped with a pallet knife and left overnight to set.

[0051] Firelighter sized fingers were cut from the block of approximate weight 35 g and size 30.5 x 62.5 x 28 mm).

[0052] Burning tests were conducted upon the firelighters so produced in quadruplicate and a control lacking vermiculite was run. Both series of samples tended to leak liquid during burning.

[0053] Thus the burning characteristics of fingers containing 2% vermiculite are not significantly impaired and the kerosene utilization per unit volume of product is improved.

Example 5

[0054] A typical artificial firelog composition was prepared by melting 72 parts of SLACKWAX 11 and admixing with slow stirring 28 parts of a mixture of sawdust (26 parts) and exfoliated vermiculite (DUPRE Grade DM) (2 parts) until uniform distribution was achieved.

[0055] The mixture was pressed into a mould as used in Example 4 and left to harden. For convenience burning tests were conducted on fingers, cut from the moulded block when cold as in Example 4 and a control lacking vermiculite was run.

[0056] Burning time per gram of slackwax 0.88 min 0.90 min

[0057] The inclusion of this grade of exfoliated vermiculite at 2% w/w level was found to reduce the density by about 3% compared with the control; the observed burning time is not significantly reduced and slackwax utilization was enhanced. Both products tended to drip slackwax slightly which is characteristic of this type of product.

[0058] A consideration of the above Examples shows that the compositions of the invention tested exhibit various surprising advantages over the controls.

[0059] First it has been found that a large reduction in density of the combustible composition may result from the addition of inorganic non-combustible particulate solid. Thus, in the case of wax/wood waste composition (Example 5 - 3% reduction) up to 9% reduction in density occurs in blocks suitable for artificial firelogs and containing little or no kerosene whilst the observed burn time (duration of burn in minutes per unit size of block material) seems not to be reduced indicating an improvement in the efficiency in the utilization of the liquefiable fuel per unit volume of product.

[0060] The reduction in density is in itself advantageous since the bigger product may be produced without using extra fuel or the existing size of product may be maintained with a fuel saving.

[0061] The corresponding reduction in density of an ignition product for use as a firelighter and prepared from an otherwise typical brown firelighter composition (Example 4 - 3% reduction) is roughly 9% on addition of 2% w/w inorganic non-combustible particulate solid and the observed burning time was not significantly decreased emphasising the increased efficiency per unit volume of the product of the fuel on incorporation of relatively low concentrations of inorganic non-combustible particulate solid.

[0062] Whilst in many cases the incorporation of inorganic solid improves the efficiency of burning of the fuel, it is at present not clear how this effect is achieved. It could be due to the structure of the inorganic non-combustible particulate solid. In the case of the more solid compositions,-the inorganic solid may merely provide a more or less rigid structure within a burning block preventing the shrinkage effect which normally accompanies burning of the block with consequent improvement of burning. Solid blocks exemplified above show an efficiency of fuel burning which tends towards the efficiency of so-called "white firelighters" in burning liquefiable fuel.

[0063] "White firelighter" is the term usually used for a firelighter composition having kerosene in liquid for encapsulated in tiny pores in a matrix of solid resin.

[0064] Again it may be due to a heat insulative effect of the inorganic non-combustible particulate solid causing reduced heat flow to the fuel in the interior of the block resulting in a reduced rate of vaporisation at the burning surface, or some combination of these effects.

Claims

1. A combustible composition which does not flow substantially during combustion comprising a fuel in the form of a wax, gel, or paste and characterised in that there is dispersed therein an inorganic, particulate, non-combustible solid serving to decrease the rate at which the fuel burns on combustion of the composition and optionally a combustible filler material; provided that when the composition comprises a combustible filler material and the composition is one which has been formed hot, the composition contains from 0.5 to 6% by weight of the inorganic, particulate, non-combustible solid.

1 2. A combustible composition as claimed in claim 1 further characterised in that the composition comprises a compacted mixture of a combustible organic solid, wax, and the inorganic, particulate, non-combustible material.

3. A combustible composition as claimed in claim 2 further characterised by comprising a combustible liquid.

4. A combustible composition as claimed in claim 1 further characterised by comprising a gelled liquid or liquefiable fuel and the inorganic, particulate, non-combustible solid.

5. A combustible composition as claimed in claim 4 and further characterised by comprising a combustible, organic solid.

6. A combustible composition as claimed in claim 2, claim 3 or claim 5 further characterised in that the said combustible, organic solid is wood waste, peat, or waste plastics, coal fines, lignite, comminuted waste paper or cardboard, or comminuted plant material.

7. A combustible composition as claimed in claim 1 and further characterised in that the composition comprises a water immiscible fuel emulsified with water to form a stiff paste and the inorganic, particulate; non-combustible solid.

8. A combustible composition as claimed in any preceding claim further characterised in that the inorganic, particulate, non-combustible solid has a bulk density of less than 0.4 g/cc.

9. A combustible composition as claimed in any one of claims 1 to 8 further characterised in that the inorganic, particulate, non-combustible solid is chalk, china clay, diatomaceous earth, perlite rock, sand, fillite, vermiculite, talc, or expanded vermiculite.

10. A combustible composition as claimed in any preceding claim further characterised by containing from 1 to 6% by weight of the inorganic particulate non-combustible solid.

ll. A firelighter or barbeque starter comprising a block of a combustible composition as claimed in any preceding claim, a sachet of a combustible composition as claimed in any preceding claim, or a tube containing a combustible composition as claimed in any preceding claim.

12. An artificial firelog comprising a combustible composition as claimed in any one of claims 1 to 10.